The inherent adhesion of many coating chemistries to various substrates, for example glass, plastics or metal, has proved to be inadequate in many technical applications. This has led in some cases to the use of primers which enable a good bond to be obtained between the coating and the substrate.
For example, in “Silane Coupling Agents”, Plueddemann et al, Plenum Press, New York (1982), aminoalkyl-alkoxysilanes have been proposed as suitable primers for polyurethanes.
Various modified aminosilanes, e.g. ketimines and aldimines of aminoalkylsilanes have been suggested, in EP 164520, for addition to polyurethane adhesives, and have been found not to impair the storage stability of the polyurethane adhesives.
The adhesion properties of coatings (e.g. finishes, paints, printing inks or adhesives) on organic and inorganic metalized substrates are also frequently inadequate. For that reason additional treatments are carried out in order to achieve satisfactory results.
The adhesion can be improved by exposing the substrates to be coated to a plasma treatment or corona treatment and then coating them, it being possible for a grafting process with e.g. acrylate monomers to be carried out between those two operations (J. Polym. Sci., Part A: Polym. Chem. 31, 1307-1314 (1993)).
It is also possible in plasmas to carry out polymerisations that result in the deposition of polymeric layers and can be used as primers, for example, H. Biederman, Y. Osada “Plasma Polymerization Processes” in “Plasma technology 3” edited by L. Holland, Elsevier, Amsterdam 1992.
WO 00/24527 discloses the plasma treatment of substrates with immediate vapour-deposition and grafting-on of photo initiators in vacuo. A disadvantage, however, is that vapour-deposition requires the use of vacuum apparatus and, because of low deposition rates, is not very efficient and is not suitable for industrial applications having high throughput rates. PCT patent application No. EP03/00780 discloses a similar process.
There is a need in the art for compositions and methods that provide for good adhesion of coatings, including inks, and laminates, to substrates such as polymers, glass and metallized substrates that can be readily practiced and are not too expensive in terms of apparatus and materials by means of which the subsequent coating of those substrates is improved.
Co-pending U.S. patent application Ser. No. 10/890,449, incorporated herein in its entirety by reference, discloses ink jet recording media comprising neutralized or partially neutralized copolymers which comprise a) at least one monomer unit derived from acrylates and acrylamides, b) at least one amine containing ethylenically unsaturated monomer and c) at least one monomer derived from polyacrylates of polyols and optionally d) an ethylenically unsaturated associative monomer.
It has been found that copolymers containing at least one monomer from each of the preceding four monomer classes, a), b), c), and d), are effective adhesion promoters allowing for better adhesion of coatings to a variety of substrates. In particular, coatings comprising said co-polymers exhibit good adhesion to, for example, polymeric substrates. Such coatings are very effective as primer layers which are subsequently coated as with a paint or ink. In the context of this invention, inks are viewed as a particular type of coating.